In March of this year, farmers in eastern and central Australia welcomed the gray weather that most city dwellers were complaining about. Water filled the dams and lakes of New South Wales and floods hit the northern part of the state, all the way up to dry areas in southern Queensland. For the first time in a decade, patches of the country's southeast had an autumn with above-average rainfall. But as the parched earth turned green, farmers were hit with yet another setback: locusts. "This is one of the best seasons that they have ever had," said Lisa Thomas of Central Darling's Livestock Health and Pest Authority. "But, unfortunately, it's all under threat."

As early as mid-August, eastern Australia may be hit with the biggest locust plague in more than 30 years. Without intervention, there could be more than $1.8 billion worth of damage to pastures, cereal crops and forage crops. Chris Adriaansen, the director of the Australian Plague Locust Commission, said that 5 million hectares of land could be affected. But he also said that Australian farmers are as prepared as they can be: aircraft contractors are organized for surveillance and insecticide aerial sprays, and farmers have been alerted to the risks. In Victoria, where the government has allocated $39.9 million to combat the plague, government authorities will have the power to enter farms and spray locusts without farmer consent. (See photographs of Australia's decade-long drought.)

The locusts have already chewed through some farmland. Heavy rainfall during the Australian summer led to higher numbers of the insects. Those that hatched in autumn managed to destroy 35,000 hectares of wheat and barley crops in Forbes Shire in central-west New South Wales. Graham Falconer, deputy mayor of Forbes, calculates $36.7 million worth of damage. Falconer believes that Australia wasn't prepared for the locusts in March and is even more worried about what will happen in August. "It's like a war," he says. "If we don't win it, we lose billions of dollars in crop."

Weather and modern farming techniques have combined to create this "perfect swarm," explains Greg Sword of the University of Sydney. Prolonged periods of warm weather allow female locusts to lay three pods (full of 50 eggs) instead of one. These days, locust eggs are able to survive longer due to direct drilling, a farming technique in which the seed is drilled directly into the unplowed soil. Twenty years ago, when plowing was more popular, the soil was turned, which exposed and, ultimately, dried the eggs. Now more are able to survive until they hatch. (Read 'Australia's Desperate Rain Dance.')

When these tiny pests exit the soil, they enter the world with the mentality of a timid grasshopper. "They are relatively sedentary; they aren't drawn to other insects," says Sword. What separates them from grasshoppers, however, is that locusts have the ability to switch between a solitary and gregarious state. It's when their antennae come into frequent contact with other locusts that they realize they are in crowded conditions and they start behaving like locusts. "They will eat everything in their path," says Falconer.

That includes eating one other. Sword and his team discovered that one of the reasons juvenile locusts swarm on the ground before they are able to fly is because they are cannibalistic. "They will happily feed on each other. So if one stops moving, he will get eaten," he says. A recent Cambridge University study of desert locusts revealed that the brain of a swarming locust was 30% larger than that of its sedentary counterpart, helping them deal with the fierce competition that exists in swarms. Sword said this could also be true of the Australian plague locust, though no studies have been done on that species yet.

Cannibals or not, these are creepy little critters. In Doris Lessing's short story "A Mild Attack of Locusts," published in the New Yorker, the protagonist describes the terror of a swarm: "The iron roof was reverberating, and the clamor of beaten iron from the lands was like thunder." Falconer says reality is no less frightening. "If you are driving along the road, it's like constantly being hit with hail. They are everywhere, when you are walking on the ground there are 40 or 50 in every square foot." For now, all that Australia's farmers can do is hope that preparation is adequate, that the locusts won't be as nightmarish as a decade of drought.